Continue to the CenterPoint Energy-Illinois Gas Transmission Company's (IGTC) customer Web site to access our tariffs and contact information. The IGTC system consists of 73 miles of 10-inch diameter pipes that extend from an interconnection with Natural Gas Pipeline Company (NGPL) in Marion County, Illinois, to Madison County, Illinois. IGTC operates as a Hinshaw pipeline under the jurisdiction of the Illinois Commerce Commission and as an interstate pipeline under the jurisdiction of the Federal Energy Regulatory Commission.